The truth about copper poisoning from Moscow mules

Head out on the town this summer and you’ll probably see it at some outdoor patio: a beverage clutched in the hands of someone who looks quite trendy, lime slices floating among ice cubes, condensation glistening on a cool, copper mug. The Moscow mule.

Moscow mules — not from Russia nor having anything to do with donkey/horse crossbreeds — are prepared with ginger beer, vodka and lime juice, and have been back in the spotlight in recent years.

However, worries have flurried after a recent news bulletin from the Iowa Alcoholic Beverages Division cast doubt on using copper mugs to serve the popular cocktail. Copper mugs have been the traditional serving method since the drink’s invention in the 1940s.

The Iowa agency adopted regulations prohibiting bars and restaurants from using copper mugs, based on FDA guidelines that suggest copper shouldn’t come into contact with foods or drinks that have a pH level below 6.0.

On the pH scale, which is used to determine the acidity of a substance, 7 is neutral. Anything below that is acidic. The ingredients of Moscow mules fall “well below” 6.0, meaning that they can leach the easily-dissolvable copper off of their container and cause the not-so-fun experience of copper poisoning in drinkers. Copper poisoning can cause diarrhea, vomiting and jaundice.

University of Massachusetts Amherst chemist Trisha Andrew spoke to Huffington Post about the realities of any potential danger in drinking Moscow mules.

“It’s been suggested that a concentration of 30 milligrams of copper per liter has been noticed to cause nausea in a small population of test subjects,” she said. “So the question is: Over the duration of time that a Moscow mule sits in a copper mug, is that enough time and acidity to leach out 30 milligrams of copper per liter?”

Her answer: no. For one, the average drinker probably won’t even drink a full liter of Moscow mules in one night. What more, nursing a drink all night is not enough time for a significant amount of copper to be leached.

“Based on the dissolution rates, it’s just nonsensical,” Andrew said. “You have to let the copper mug sit in straight lime juice for a few hours before you can even start to begin to worry about [copper poisoning].”

Another reason you can probably relax and enjoy your drink: Many bars and restaurants already serve the cocktail in copper cups safely lined with tin or stainless steel.